Central London construction activity has picked up with 25 construction starts in the past six months, according to Drivers Jonas Deloitte's Winter 2012 Crane Survey.

This takes the total amount of office space under construction in London up to 9m sq ft.

Nine new schemes are currently under construction in the City, representing a 15% increase on the past six months. A total of 4.1m sq ft is now under construction, the first time that construction has risen by about 4m sq ft since Q1 2009.

Construction in the West End slowed, with eight new starts totalling 270,500 sq ft during the six-month period. Total space under construction in the West End now stands at 2.3m sq ft, a 14% drop from the previous crane survey.

Anthony Duggan, head of research and partner with Drivers Jonas Deloitte, said: "Construction levels across central London have remained steady at 9m sq ft, with the level of completions matched by 25 new starts totalling 1.5m sq ft.

"At a market level, the City has seen a further increase in construction, while a number of development completions and a lower level of new starts have led to activity falling in the West End.

"Developers have been encouraged by increased letting activity among the schemes under construction with several schemes having achieved early-letting success over the past six months.

"We expect additional letting activity to be announced over the next few months - reducing further the volume of available space that is being delivered."